when you plug in your ipod your itunes account should automaticly open. have limewire or window media player already open aswell and you should be able to just drag and drop the songs into itunes.
If that doesnt work, when you are in your itunes account go to the top left hand corner and click file, then click on import. This will open your music file in your docments and you should have all your saved downloaded music there, just highlight it and click import.